Reimplement ECal using ECalClient.
Reimplement ECal using ECalClient.

This is primarily so I don't have to duplicate work while overhauling
the D-Bus API, but it's good to do anyway; it simplifies the deprecated
logic and helps ensure the two APIs behave consistently.

matzipan/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,Distrotech/evolution-data-server,tintou/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server,Distrotech/evolution-data-server,Distrotech/evolution-data-server,matzipan/evolution-data-server,matzipan/evolution-data-server,tintou/evolution-data-server,tintou/evolution-data-server,matzipan/evolution-data-server